The function of the TCAS display is to present air traffic information, declare threats, and provide advisories on potential air traffic conflicts before the closest point of approach. The TCAS display of the related art uses two-dimensional graphics to convey traffic information in the own aircraft's own protected volume of airspace. However, since two-dimensional graphics can only depict information on two (X- and Y-axes) of the three dimensions required to completely represent spatial traffic relationships for TCAS (X-, Y-, and Z-axes), numerics are used to portray relative altitude on the Z-axis. This two-dimensional plan view display of the TCAS traffic information (supplemented with numeric data tags for the third dimension, altitude) does not provide a direct visual display of the dynamic spatial relationships existing between air traffic in the natural three-dimensional airspace. Interpretation of such a display requires considerable time and mental effort, in that it requires pilots to mentally construct a three-dimensional image of the traffic situation by combining graphically displayed azimuth and range information with numerically presented altitude information.
The related art TCAS display, therefore, is limited to function as an aid to direct visual acquisition of target aircraft, rather than as a correct, veridical, and easily interpretable complete "picture" of the current traffic situation. Pilots simply use the presented information as a cue for visual search to locate potential threats by direct visualization of aircraft outside the cockpit. Furthermore, since the traffic information is dynamic and continuously updated, direct visualization will require pilots to continuously alternate their attention from reading the numerics on the head-down TCAS display to the head-up search up for aircraft outside the cockpit. Thus, using the related art TCAS display, pilots often find it time-consuming and confusing to visually acquire and process dynamic changes in the air traffic situation under moderate or high cockpit workload situations.
Attempts of the related art to solve the problems of indirect visualization of conventional displays have focussed on basic symbology refinement for the two-dimensional TCAS display format. Efforts have been made to reduce confusion and misinterpretation by modifying the symbols. For example, all the numeric codes were initially displayed above the aircraft symbol with a "+" or "-" sign to indicate relative elevation. The most current baseline TCAS display presents the numerics either above or below the symbol for conceptual compatibility. No effort has been made to explore other innovative approaches or to empirically validate current design concepts. However, research on display formats for other applications reveals potential benefits of an innovative three-dimensional perspective format. Ground-based perspective traffic display formats have been studied in the related art to demonstrate the advantages of utilizing perspective graphics for portraying complex spatial situations. Additionally, perspective displays for naval battlefield management systems have been previously studied to examine the feasibility and advantages of three-dimensional graphic presentations. Such studies have shown significant advantages of three-dimensional formats over two-dimensional formats.